The invention relates to a cutter for cutting spherical seats in metallic workpieces.
Depicted in FIG. 1 is a prior art spherical seat cutter 20a of the type described in Peuterbaugh U.S. Pat. No. 5,232,317. The seat cutter 20a cuts a spherical seat S on the interior of a workpiece such as a differential casing D which is fixedly held. Suitable article handling apparatus, not shown, transfers the casing D to and from the work station shown in FIG. 1 in a direction 10 perpendicular to the paper. The casing D has diametrically aligned bores B around which the seats S are cut, as well as a large opening O at its top. The cutter 20a is supported for rotation about its central axis by a hanger 22a which is in turn mounted for vertical and horizontal movement. Cutter 20a includes a steel cutter body 26a formed with a reduced diameter section 28a at its rearward end which is rotatably supported within a bore 30a through hanger 22a. A removable retainer plate 32a detachably coupled to the rearward end of the reduced diameter section 28a of the cutter body retains the cutter against axial movement relative to hanger 22a.
In the tooling arrangement shown in FIG. 1, a single-ended cutter cuts the seat at one side of the differential case at the work station. An alternative arrangement could be provided which utilizes a double-ended cutter, i.e., with a like second body portion 26a projecting from the opposite end of reduced diameter section 28a, initially to cut one seat and then the other seat.
A rotatable drive arbor 34 projects through a central passage 36a extending through cutter 20a and is rotatably supported at opposite sides of the differential casing D by stationary bearing assemblies 38a and 40a. The arbor 34a is formed with splines engageable with complementary splines formed within the central passage 36a. The arbor 34a is coupled to a suitable drive mechanism which is operable to drive the arbor in rotation and to also shift the arbor horizontally.
The cutting of the seat in the workpiece D is performed by indexible cutting inserts 42a detachably mounted in the cutter. The inserts 42a include substantially parallel main surfaces 44a intersected by end surfaces 46a to form cutting edges 48a. The inserts 42a are mounted by fastener screws 50a in recesses formed in a front end surface F of the steel body 26a of the cutter 20a such that the main surfaces 44a lie in planes intersecting the front end surface F. The fastener screws 50a extend tangentially with respect to the axis of rotation.
The cutter 20a may be susceptible to fracture at regions A disposed between the central passage 36a and respective inserts 42a, because the thickness of the steel of the body 26a there is minimal and may not be able to withstand the forces generated at high rpm's.